1,072 research outputs found
Flight Flutter Testing of Supersonic Interceptors
A summary is presented of experiences in connection with flight flutter testing of supersonic interceptors. The planning and operational aspects involved are described along with the difficulties encountered, and the correlation between measurement and theory. Recommendations for future research and development to advance the science of flight flutter testing are included
Feasibility study of an Integrated Program for Aerospace-vehicle Design (IPAD) system. Volume 6: Implementation schedule, development costs, operational costs, benefit assessment, impact on company organization, spin-off assessment, phase 1, tasks 3 to 8
A baseline implementation plan, including alternative implementation approaches for critical software elements and variants to the plan, was developed. The basic philosophy was aimed at: (1) a progressive release of capability for three major computing systems, (2) an end product that was a working tool, (3) giving participation to industry, government agencies, and universities, and (4) emphasizing the development of critical elements of the IPAD framework software. The results of these tasks indicate an IPAD first release capability 45 months after go-ahead, a five year total implementation schedule, and a total developmental cost of 2027 man-months and 1074 computer hours. Several areas of operational cost increases were identified mainly due to the impact of additional equipment needed and additional computer overhead. The benefits of an IPAD system were related mainly to potential savings in engineering man-hours, reduction of design-cycle calendar time, and indirect upgrading of product quality and performance
Urinary diversion and bladder reconstruction/replacement using intestinal segments for intractable incontinence or following cystectomy
Background Surgery performed to improve or replace the function of the diseased urinary bladder has been carried out for over a century. Main reasons for improving or replacing the function of the urinary bladder are bladder cancer, neurogenic bladder dysfunction, detrusor overactivity and chronic inflammatory diseases of the bladder (such as interstitial cystitis, tuberculosis and schistosomiasis). There is still much uncertainty about the best surgical approach. Options available at the present time include: (1) conduit diversion (the creation of various intestinal conduits to the skin) or continent diversion (which includes either a rectal reservoir or continent cutaneous diversion), (2) bladder reconstruction and (3) replacement of the bladder with various intestinal segments. Objectives To determine the best way of improving or replacing the function of the lower urinary tract using intestinal segments when the bladder has to be removed or when it has been rendered useless or dangerous by disease. Search methods We searched the Cochrane Incontinence Group Specialised Trials Register (searched 28 October 2011), which contains trials identified from the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE and CINAHL, and handsearching of journals and conference proceedings, and the reference lists of relevant articles. Selection criteria All randomised or quasi-randomised controlled trials of surgery involving transposition of an intestinal segment into the urinary tract. Data collection and analysis Trials were evaluated for appropriateness for inclusion and for risk of bias by the review authors. Three review authors were involved in the data extraction. Data were combined in a meta-analysis when appropriate. Main results Five trials met the inclusion criteria with a total of 355 participants. These trials addressed only five of the 14 comparisons pre-specified in the protocol. One trial reported no statistically significant differences in the incidence of upper urinary tract infection, uretero-intestinal stenosis and renal deterioration in the comparison of continent diversion with conduit diversion. The confidence intervals were all wide, however, and did not rule out important clinical differences. In a second trial, there was no reported difference in the incidence of upper urinary tract infection and uretero-intestinal stenosis when conduit diversions were fashioned from either ileum or colon. A meta-analysis of two trials showed no statistically significant difference in daytime or nocturnal incontinence amongst participants who were randomised to ileocolonic/ileocaecal segment bladder replacement compared to an ileal bladder replacement. However, one small trial suggested that bladder replacement using an ileal segment compared to using an ileocolonic segment may be better in terms of lower rates of nocturnal incontinence. There were no differences in the incidence of dilatation of upper tract, daytime urinary incontinence or wound infection using different intestinal segments for bladder replacement. However the data were reported for 'renal units', but not in a form that allowed appropriate patient-based paired analyses. No statistically significant difference was found in the incidence of renal scarring between anti-refluxing versus freely refluxing uretero-intestinal anastomotic techniques in conduit diversions and bladder replacement groups. Again, the outcome data were not reported as paired analysis or in form to carry out paired analysis. Authors' conclusions The evidence from the included trials was very limited. Only five studies met the inclusion criteria; these were small, of moderate or poor methodological quality, and reported few of the pre-selected outcome measures. This review did not find any evidence that bladder replacement (orthotopic or continent diversion) was better than conduit diversion following cystectomy for cancer. There was no evidence to suggest that bladder reconstruction was better than conduit diversion for benign disease. The clinical significance of data from one small trial suggesting that bladder replacement using an ileal segment compared to using an ileocolonic segment is better in terms of lower rates of nocturnal incontinence is uncertain. The small amount of usable evidence for this review suggests that collaborative multi centre studies should be organised, using random allocation where possible. This review is published as a Cochrane Review in the Cochrane Database of Systematic Reviews 2012, Issue 2. Cochrane Reviews are regularly updated as new evidence emerges and in response to comments and criticisms, and the Cochrane Database of Systematic Reviews should be consulted for the most recent version of the Review.</p
Trions in monolayer transition metal dichalcogenides within the hyperspherical harmonics method
We develop the theoretical formalism and study the formation of valley trions
in transition metal dichalcogenide (TMDC) monolayers within the framework of a
non-relativistic potential model using the method of hyperspherical harmonics
(HH) in four-dimensional space. We present the solution of the three-body
Schr\"{o}dinger equation with the Rytova-Keldysh (RK) potential by expanding
the wave function of a trion in terms of the HH. The antisymmetrization of
trions wave function is based on the electron and hole spin and valley indices.
We consider a long-range approximation when the RK potential is approximated
by the Coulomb potential and a short-range limit when this potential is
approximated by the logarithmic potential. In a diagonal approximation, the
coupled system of differential equations for the hyperradial functions is
decoupled in both limits. Our approach yields the analytical solution for
binding energy and wave function of trions in the diagonal approximation for
these two limiting cases - the Coulomb and logarithmic potentials. We obtain
exact analytical expressions for eigenvalues and eigenfunctions for negatively
and positively charged trions. The corresponding energy eigenvalues can be
considered as the lower and upper limits for the trions binding energies.
The proposed theoretical approach can describe trions in TMDCs and address
the energy difference between the binding energies of and in
TMDC. Results of numerical calculations for the ground state energies with the
RK potential are in good agreement with similar calculations and in reasonable
agreement with experimental measurements of trion binding energies.Comment: 21 pages, 6 figure
The zinc finger transcription factor PLAGL2 enhances stem cell fate and activates expression of ASCL2 in intestinal epithelial cells
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Towards precision medicine for hypertension: a review of genomic, epigenomic, and microbiomic effects on blood pressure in experimental rat models and humans
Compelling evidence for the inherited nature of essential hypertension has led to extensive research in rats and humans. Rats have served as the primary model for research on the genetics of hypertension resulting in identification of genomic regions that are causally associated with hypertension. In more recent times, genome-wide studies in humans have also begun to improve our understanding of the inheritance of polygenic forms of hypertension. Based on the chronological progression of research into the genetics of hypertension as the "structural backbone," this review catalogs and discusses the rat and human genetic elements mapped and implicated in blood pressure regulation. Furthermore, the knowledge gained from these genetic studies that provide evidence to suggest that much of the genetic influence on hypertension residing within noncoding elements of our DNA and operating through pervasive epistasis or gene-gene interactions is highlighted. Lastly, perspectives on current thinking that the more complex "triad" of the genome, epigenome, and the microbiome operating to influence the inheritance of hypertension, is documented. Overall, the collective knowledge gained from rats and humans is disappointing in the sense that major hypertension-causing genes as targets for clinical management of essential hypertension may not be a clinical reality. On the other hand, the realization that the polygenic nature of hypertension prevents any single locus from being a relevant clinical target for all humans directs future studies on the genetics of hypertension towards an individualized genomic approach
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Investigating 2D semiconductor contacts for Cooper-pair light-emitting diode applications
Future quantum technologies will require high-efficiency, on-demand sources of entangled photons. A possible route to building such light sources employs two-dimensional (2D) semiconductors interfaced with a source of Cooper pairs. To investigate the possibility of such devices, we are testing methods to make high transparency n-type contacts, p-type contacts, and superconducting contacts to 2D semiconductors. For example, following the pioneering work of Liu et al., we are testing transferred metal contacts [1]. By placing the preformed metal on top of the 2D semiconductor, a pristine interface can be achieved, in contrast to evaporated metal contacts that typically generate defects at the interface. We will present preliminary results from our experiments.
[1] Y. Liu, J. Guo, E. Zhu, L. Liao, S.-J. Lee, M. Ding, I. Shakir, V. Gambin, Y. Huang & X. Duan, “Approaching the Schottky–Mott limit in van der Waals metal–semiconductor junctions”, Nature 557, 696-700 (2018)
Intelligence and video games
This study aims to determine describe the perceived relationship between video games and intelligence among the selected individuals. The study makes use of the video game “BRAIN AGE” as one of the tools of the research. Responses of the informants showed that video games can slightly contribute to mental development and a new theory was developed the “Dublin game attention theory” where as a person grows older his time to attention span for playing video games becomes more shorter but does not necessarily reflect a loss of interest in the gaming hobby
Leaning Right and Learning from the Left: Diffusion of Corporate Tax Policy in the OECD
There is an increased focus in comparative politics and international relations on how choices of national governments are dependent on choices made by governments in other countries. We argue that while the relationship between policy choices across countries is often labeled as either diffusion or competition, in many cases the theoretical mechanisms underpinning these labels are unclear. In this paper we build a model of social learning with a specific application to the diffusion of corporate tax reductions. This model yields predictions that are differentiable from existing models of tax competition. Specifically, we argue that social learning is most likely to take place in the wake of tax policy cuts by left governments. We test this model using an existing data set of corporate tax rate changes and an author-created data set of changes in tax legislation, covering twenty OECD countries from 1980-1998.
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